Blanket-type thermal insulation is frequently used for commercial and industrial applications that require personnel protection or thermal insulation. Such blankets are typically flexible, removable, and reusable to a greater or lesser degree. A drawback of most commonly-used insulation blankets is that they are prone to absorbing and holding moisture when exposed to a moisture source, whether in indoor or outdoor environments. Retention of moisture is undesirable because wet blankets lose much of their thermal insulation ability, they become heavier, and they can sag. The ingress and accumulation of water not only affect the insulating properties of the blanket, and the position of the blanket relative to the object being insulated, but can potentially lead to under-insulation-induced corrosion or moisture-induced corrosion on the insulated equipment, which can affect safety and system life.
There is an unfilled need for improved, economical, hydrophobic thermal insulation materials with improved long-term thermal performance, and resistance to corrosion when used in high-temperature, humid environments.
Several types of insulation blankets are currently available commercially, including those made from mineral wool, aerogels, fiberglass, and microporous insulation. Some of these materials address or partially address water intrusion and absorption by employing a water repellent (hydrophobic) treatment. However, hydrophobicity in high temperature (>400° F., 205° C.) blanket materials is rare. In most cases, hydrophobicity decays over time or upon exposure to temperatures in excess of 300° F. (150° C.), creating thermal inefficiency, personnel safety risk, and corrosion issues.
Water inside an insulation material compromises insulation characteristics, regardless of the type of insulation material. Water inside insulation is also a key factor in the corrosion of covered metallic equipment.
Mineral wools and fiberglass wools can hold large amounts of water after they have been submerged in water, or even without submersion after extended exposure to water vapor/steam. Hydrophobic wools, blankets, boards, or roll materials (example: Johns Manville MinWool-1200) can be treated with a water-repelling agent such as a liquid silicone emulsion or like, which can be integrated into the product during processing or sprayed onto its surface. These agents typically have a limited life expectancy, depending on service conditions. They may or may not pass initial (“as new”) accepted industry standards for hydrophobicity (e.g. ASTM C 1511-15).
A microporous insulation blanket/panel is a high-temperature, thin, flexible, blanket insulator incorporating hydrophobic, fumed silica particles to attain hydrophobicity to 600° F. (315° C.). Examples are Johns Manville InsulThin™ HT and Microtherm® Quilted Panels. A disadvantage of these materials is that they generate substantial amounts of dust during product application and fabrication. Dust can also be released from these products when the hydrophobic woven E-glass cloth outer envelope is cut or damaged.
Commercially-available aerogel blanket products generally meet the hydrophobicity requirements of ASTM C 1511. However, aerogel blankets often have excess caking resulting from their processing. Caked, excess aerogel material left on the surface can generate dust during handling and application. This nuisance dust can cause applicators to incur added fabrication, installation, and application precautions, with attendant increased expense. With both microporous insulation and aerogel blankets, the generation of dust is difficult to avoid, and is a major inconvenience for operators working with or in the vicinity of such materials.
Thermiguard™ SS D 0713 Submittal Sheet (unknown date) discloses thermal blankets in which the insulation material is a fiberglass needled mat type E fiber mat, encapsulated by PTFE-impregnated fiberglass cloth.
L. Dill, “The Right Stuff: Material Considerations,” Insulation Outlook (June 2004) describes various high-temperature insulation blankets, including some made from a fiberglass felt core insulation with a silicone- or PTFE-impregnated fiberglass fabric exterior for waterproofing.
U.S. patent application publication no. 2011/0070789 discloses a laminate material with layers combined into an insulating barrier blanket. The insulating barrier blanket comprises a high-temperature, abrasive and puncture resistant outer shell, a thermal insulation core, and an interior protective layer. The outer shell is preferentially made of a hydrophobic or oleophobic fabric layer, such as organic polyamide fibers or PTFE-laminated fiberglass.
Thermablock Aerogel Insulation Blanket (unknown date) is a data sheet for a commercially available product, describing a silica aerogel insulation blanket said to be vapor-permeable, but nonhygroscopic offering no transport for liquid.
There is an unfilled need for an insulation material that is hydrophobic to temperatures of 600° F. (315° C.) for long-term use (or higher temperatures during short excursions), that does not produce dust during installation and use, and that is more economical than existing insulators.